American Heart Association's Guidelines for Diagnosing Hypertension
According to the American Heart Association/American College of Cardiology (AHA/ACC) guidelines, hypertension is defined as blood pressure ≥130/80 mm Hg, classified into stages based on severity, with diagnosis requiring proper measurement technique and often confirmation with out-of-office readings. 1
Blood Pressure Classification
The AHA/ACC guidelines define the following blood pressure categories:
| Category | Systolic Blood Pressure | Diastolic Blood Pressure |
|---|---|---|
| Normal | <120 mm Hg | and |
| Elevated | 120-129 mm Hg | and |
| Stage 1 Hypertension | 130-139 mm Hg | or |
| Stage 2 Hypertension | ≥140 mm Hg | or |
This classification represents a significant change from previous guidelines, as it lowered the threshold for hypertension diagnosis from ≥140/90 mm Hg to ≥130/80 mm Hg 1. This change was based on evidence showing that adults with BP in the 130-139/80-89 mm Hg range have approximately a 2-fold increase in cardiovascular disease risk compared to those with normal BP 1.
Proper Blood Pressure Measurement Technique
Accurate diagnosis requires proper measurement technique:
- Measurements should be taken after 5 minutes of quiet rest
- Patient should be seated with back supported and feet flat on the floor
- Arm should be supported at heart level
- Appropriate cuff size must be used
- At least 2 readings should be taken at intervals of 1-2 minutes
- Average of ≥2 readings obtained on ≥2 separate occasions 1
Out-of-Office Blood Pressure Confirmation
The AHA/ACC guidelines emphasize the importance of out-of-office BP measurements to confirm diagnosis and detect:
- White coat hypertension: High office BP but normal out-of-office BP
- Masked hypertension: Normal office BP but high out-of-office BP
Out-of-office measurements can be obtained through:
- Ambulatory BP monitoring (ABPM): 24-hour monitoring with measurements taken at regular intervals
- Home BP monitoring (HBPM): Patient self-monitoring with validated devices
The guidelines provide equivalence values between office and out-of-office readings:
| Office BP | Home BP | Daytime ABPM | Nighttime ABPM | 24-hour ABPM |
|---|---|---|---|---|
| 120/80 | 120/80 | 120/80 | 100/65 | 115/75 |
| 130/80 | 130/80 | 130/80 | 110/65 | 125/75 |
| 140/90 | 135/85 | 135/85 | 120/70 | 130/80 |
| 160/100 | 145/90 | 145/90 | 140/85 | 145/90 |
Impact on Hypertension Prevalence
This redefinition of hypertension has increased the estimated prevalence of hypertension in the US adult population from 32% to approximately 46% 1, 2. However, this change only resulted in a small increase (1.9%) in adults requiring antihypertensive medication therapy, as most newly diagnosed individuals are recommended for nonpharmacological interventions 1, 3.
Special Considerations
- Age differences: Prevalence estimates using the new definition are more discrepant at younger ages than at older ages 1
- Gender differences: The new definition affects men more than women 1
- Racial/ethnic differences: Hypertension prevalence is higher in non-Hispanic blacks (59%) compared to non-Hispanic whites (47%), non-Hispanic Asians (45%), and Hispanics (44%) 1, 2
Common Pitfalls in Hypertension Diagnosis
Single-visit diagnosis: Guidelines recommend BP measurements on ≥2 separate occasions; single-visit measurements may overestimate hypertension prevalence 1
Improper measurement technique: Incorrect cuff size, patient positioning, or insufficient rest time can lead to inaccurate readings
Failure to detect white coat or masked hypertension: Out-of-office measurements are essential to confirm diagnosis and guide treatment decisions 1
Ignoring BP variability: BP naturally fluctuates throughout the day; multiple measurements provide a more accurate assessment
By following these guidelines, clinicians can accurately diagnose hypertension and identify patients who would benefit from lifestyle modifications or pharmacological intervention to reduce cardiovascular risk.